/Engine/Source/Runtime/SlateCore/Public/Input/HittestGrid.h
AddSWidgetfrom the HitTest Grid
void AddWidget ( const [TSharedRef](API\Runtime\Core\Templates\TSharedRef)< [SWidget](API\Runtime\SlateCore\Widgets\SWidget) > & InWidget, int32 InBatchPriorityGroup, int32 InLayerId, int32 InSecondarySort )